1. Technical Field
The present invention relates generally to radio telecommunication networks. More specifically, the present invention relates to the prevention and elimination of radio frequency (RF) link failures in a radio telecommunication network through an adaptive failure handling algorithm.
2. Background Information
In a radio telecommunication network a subscriber unit (SU) is able to communicate with the telecommunication network through the use of radio frequency (RF) signals. The radio telecommunication network includes a plurality of RF transceivers or base stations and a plurality of RF SU's. The SU's utilize a RF link to register with, and maintain connection to, the telecommunication network.
The present radio telecommunication networks suffer from areas of poor RF signal strength which can cause the RF link between a SU and a base station to fail. Such RF link failures occur when the voice or data quality of the SU is unacceptable and cannot be improved by RF power control or by a hand off from one base station to another.
Environmental conditions can cause RF link failures due to loss of RF coverage or excessive co-channel interference or a combination of both. Such RF link failures due to loss of RF coverage or excessive co-channel interference or a combination of both can be caused by natural or man-made environmental conditions.
Such environmental conditions can include open areas, flat areas, hilly areas, mountainous areas, buildings, houses, bridges, tunnels, rural areas, quasi-suburban areas, suburban areas and urban areas as well as combinations of the above. The above environments can cause long term fading, local-mean attenuation and fluctuations as well as short term or transitory fluctuations in RF signal strength. Many RF link failures are transitory in nature. One example of a RF link failure may be in an urban environment with many buildings where merely turning a corner can result in as much as a 30 dB loss in the RF signal strength.
When a RF link failure occurs the SU scans for an available channel or frequency to re-establish the RF link and to re-register with the network. If the RF link failure was transitory the SU will likely re-establish the RF link using the same frequency or channel. Such scanning and re-registering is undesirable because it requires additional power for the repeated scanning and re-registration which can rapidly drain the SU's batteries and decrease network capacity. In addition to the undesirable effects on battery life and network capacity, if RF link failure occurs when the SU has a call in progress, the call may have to be placed again.
The present invention seeks to increase the satisfaction of radio telecommunication network subscribers and the efficiency of the network by minimizing the number and duration of RF link failures which also decreases the demands on both the SU's battery life as well as the network's capacity.